Correlated Simulation of Pseudo Transient Torque Converter Clutch Engagement Using Coupled Fluid Structure Interaction

This investigation utilizes a correlated fluid-structure interaction (FSI) model of the torque converter and clutch assembly to perform a pseudo transient clutch engagement at steady state operating conditions. The pseudo transient condition consists of a series of nine steady state simulations that transition the torque converter clutch from fully released to near full lockup at a constant input torque and output speed representative of a highway cruising speed. The flow and pressured field of the torque converter torus and clutch are solved using a CFD model and then passed along to a transient structural model to determine the torque capacity of the lockup clutch. Bulk property assumptions regarding the friction material, deformation of the clutch plate, and deflection of supporting structures were made to simplify the model setup, run time, and solution convergence. Telemetry pressure measurements acquired in an operating torque converter under similar operating conditions on a transmission dynamometer test stand are provided to demonstrate FSI model correlation and behavior. A total of nine steady-state speed ratio simulations were run, from fully released to nearly fully locked torque converter clutch with less than 5% error in predicted pressure values compared with measured telemetry data. Visualization of the transmission fluid behavior within the torque converter pressure vessel during the engagement of the clutch from released to less than 10 rpm slip condition are provided. The overall objective of the investigation was to seek out and identify any potential fluid phenomena that contribute to undesirable control of the lockup clutch at low slip speed ratios.